EP0011183B1 - Process for the isolation of phenol-formaldehyde resins containing boron - Google Patents

Description

The present invention relates to a process for isolating boron-containing phenol-formaldehyde resins from their reaction media.

DE-OS 2 557 613 describes boron-containing phenol-formaldehyde resins which can be prepared by partially reacting a novolak with boron compounds and simultaneous or subsequent reaction with unsaturated fatty acids.

In dieser Formel bedeuten

• m, n Werte zwischen 1 und 2 mit der Bedingung m + n = 2,
• A C_l-C_4-Alkyl wie Methyl, Äthyl, Propyl, Butyl, Isopropyl, Isobutyl,
• R, A oder X
• X ein Novolak, der durch Kondensation eines Aldehyds mit einem Diphenylolalkan oder einem Gemisch aus Diphenylolalkanen und Hydroxyphenyl-hydroxyindan- und Hydroxyphenyl-hydroxychroman-Isomeren in Gegenwart saurer Katalysatoren gebildet wird und der noch freie phenolische OH-Gruppen sowie eine ungesättigte Fettsäure mit bevorzugt C_12-C₃, C-Atomen, oder Gemische davon, einkondensiert, enthält.

These resins can be represented by the following formula:

Mean in this formula

• m, n values between 1 and 2 with the condition m + n = 2,
• AC ₁ -C ₄ alkyl such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl,
• R, A or X
• X is a novolak which is formed by condensation of an aldehyde with a diphenylolalkane or a mixture of diphenylolalkanes and hydroxyphenyl-hydroxyindane and hydroxyphenyl-hydroxychroman isomers in the presence of acidic catalysts and which still has free phenolic OH groups and an unsaturated fatty acid, preferably C _{12 -} C ₃ , C atoms, or mixtures thereof, condensed.

The boron-containing resins are soluble in methanol, ethanol, propanol, isopropanol, butanol, isobutanol, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, methyl and ethyl glycol acetate and have an iodine number of 80 to 200, preferably 110 to 170 and one OH number from 200 to 500, preferably from 240 to 450, and have a boron content of up to 7% by weight, preferably 1.5 to 5% by weight. The softening point range of the resins is between 50 and 150 ° C, preferably between 55 and 110 ° C.

After the reaction to give the boron-containing resins, the reaction medium consists of the end product obtained, the starting compounds used and the solvents used.

As described in DE-OS 2 557 613, the novolaks are reaction products of diphenylolalkanes, as are mentioned, for example, in DT-AS 1 235 894. Hydroxyphenyl-hydroxyindanes or mixtures thereof with aldehydes are used as the starting product. Other starting products are fatty acid or its esters, boron trioxide, boric acid and alkyl borate esters of the formulas:

Another component of the reaction medium consists of the solvent used in the reaction, such as benzene, toluene, xylene, ethyl acetate, butyl acetate, methyl glycol or ethyl glycol acetate, and alcohols with 1-4 C atoms.

• a) durch Eindampfen der Harzlösung im Reaktionskessel und Ablassen der flüssigen Harzschmelze,
• b) durch Eindampfen der Harzlösung vermittels einer Ausdampfschnecke als auch
• c) durch Eindampfen der Harzlösung in einem Schlangenrohrverdampfer erfolgen,

wobei alle 3 Aufarbeitungsvarianten für gleichbedeutend gehalten werden.The isolation of the boron-containing phenol-formaldehyde resins can both

• a) by evaporating the resin solution in the reaction vessel and draining the liquid resin melt,
• b) by evaporating the resin solution using an evaporation screw as well
• c) by evaporating the resin solution in a coiled tube evaporator,

whereby all 3 processing variants are considered synonymous.

The phenol-formaldehyde resins modified with boric acid esters can be used as reinforcing resins for rubbers. For this purpose, they are in the presence of a formaldehyde-releasing compound such as hexamethylenetetramine, paraformaldehyde, trioxi or tetraoxymethylene on the mixing units customary in rubber processing such as e.g. Rolling mills, kneaders and high-speed mixers mixed into rubber at elevated temperatures.

However, the valuable properties of the boric acid ester-modified phenol-formaldehyde resins, namely their high temperature-resistant hardness in various rubbers with simultaneous increase in structural strength and their universal usability in various synthetic rubbers such as NBR, SBR, EPDM, BR, CR and NR, are only optimally achieved, if, on the one hand, the solvent used in the production can be removed as completely as possible, and on the other hand, the boron compound used can be esterified as quantitatively as possible into the novolak without reducing its advantageous high reactivity due to partially crosslinking condensation due to excessive thermal stress.

It was found that, owing to the high reactivity of the trifunctional boric acid ester compounds, it is not possible to isolate the resin in a commercially viable size by evaporation in the reaction vessel, largely without solvent and uncrosslinked. Due to the longer distillation times for the solvent, the resin must be isolated from the reaction vessel prematurely, in order to avoid crosslinking due to excessive temperature stress, without the solvent being able to be removed completely. As a result, the advantageous properties of the resin are not optimally achieved; - You get hardened rubber materials with less high hardness values. The resins thus obtained are not sufficiently stable in storage. They gradually sinter together, lose their packaging form and, when incorporated into the rubber, cause the rubber mixture to stick to the mixing rollers due to the residual solvent content. While the resin can still be isolated from smaller reaction vessels with a content of up to 0.2 m ³ due to the lower temperature load during direct evaporation, this is no longer possible for larger technical reaction vessels for the reasons mentioned above.

The continuous evaporation of the reinforcement resin solution in an evaporation screw economically reasonable size (throughput: 80-500 kg / h; residence time: 15-30 min.) Resins are also obtained, which have the optimal properties after a short thermal load from a smaller evaporation screw (throughput : 1-10 kg / h) do not reach insulated reinforcement resin. If you want to isolate solvent-free resins using this process, you always get partially cross-linked products that do not melt completely when mixed into the rubber (specks) and do not distribute themselves homogeneously in the rubber matrix. The hardened rubber materials consequently show reduced hardness and lower structural strength.

In order to be homogeneously mixed and melted into the rubber by this process. Obtaining bare resins, one has to do without a complete evaporation of the solvent. The resins thus obtained have low softening points (Ep. 40-60 ° C; according to DIN 53180), cause sticking when mixed into the rubber and provide hardened rubbers of reduced hardness. When stored for a long time, such resins sinter together so that they are difficult to process technically.

• 1. Das Harz soll hohe temperaturstabile Härtewerte der gehärteten Kautschukmaterialien liefern.
• 2. Die durch Einmischen des Harzes gehärteten Kautschukmaterialien sollen hohe Strukturviskositäten aufweisen.
• 3. Die Harze sollen bei Verarbeitungstemperaturen von 70 bis 120°C, vorzugsweise von 80 bis 100°C, universell in verschiedene synthetische Kautschuke wie NBR, SBR, EPDM, BR, CR, sowie Naturkautschuk unter Ausbildung gehärteter Kautschukmaterialien der unter 1. und 2. genannten vorteilhaften Eigenschaften einarbeitbar sein.
• 4. Die Harze sollen innerhalb des genannten Verarbeitungstemperaturbereiches aufschmelzen und sich homogen in der Kautschukmatrix verteilen lassen ohne Kleben an den Einmischwalzen zu verursachen.

The object of the invention was to find a process which allows the isolation and final assembly of the resins from their solution, the properties of the resins listed below being achieved as optimally as possible:

• 1. The resin should provide high temperature-stable hardness values of the hardened rubber materials.
• 2. The rubber materials hardened by mixing in the resin should have high intrinsic viscosities.
• 3. The resins should be universally at processing temperatures of 70 to 120 ° C, preferably from 80 to 100 ° C, in various synthetic rubbers such as NBR, SBR, EPDM, BR, CR, and natural rubber with the formation of hardened rubber materials of 1 and 2 can be incorporated advantageous properties mentioned.
• 4. The resins should melt within the processing temperature range mentioned and be homogeneously distributed in the rubber matrix without causing sticking to the mixing rollers.

In order to achieve these properties optimally, it was necessary to find a work-up method for the resin solution which caused the boron compound added to be largely condensed into the novolak base body of the resin and which also carried out a quantitative removal of the Solvent allowed, without resulting in a condensation reaction proceeding to partial crosslinking of the resin due to excessive thermal stress.

The object of the invention was therefore to determine a workup method which allows the parameter dwell time to be made adjustable by the parameters temperature and pressure such that the resins obtained by the workup process according to the invention have the above-mentioned. have significant advantageous properties 1. to 4. and that these resins are not exposed to any influences damaging their positive properties during processing.

This could be achieved by evaporation of the resin solution in a coiled reaction and evaporation tube, or snake tube for short, with a specific ratio of throughput to flow cross-section, hereinafter referred to as A, and a specific ratio of throughput to heat transfer surface, hereinafter referred to as B, according to the invention .

vorzugsweise 0,2 bis 0,5 und

vorzugsweise von 150 bis 300.The invention thus relates to a process for the isolation of boron-containing phenol-formaldehyde resins from their reaction media which, in addition to the end product, also contain starting compounds and solvents, which is characterized in that the isolation is carried out by evaporation in a coiled evaporation tube, which has the following characteristics:

preferably 0.2 to 0.5 and

preferably from 150 to 300.

In the event of deviations from these ratios, resins are obtained which do not have the desired optimal properties 1 to 4. If one chooses B too small at constant A, that is, at constant flow rate, a resin is obtained which has a high boron content, but which has a high degree of crosslinking due to the thermal load during evaporation.

If the value for B is too large for constant A, the evaporation is not complete and the boron content of the resin is too low, so that the product corresponds essentially to that of an incomplete boiler evaporation.

The evaporation can also run into the coil tube with the addition of additional gas, such as nitrogen or carbon dioxide. However, this is only necessary if overheating of the solution should be avoided in front of the snake tube for reasons of product stability. If overheating is possible, no additional gas is required since the initial speed is high enough to meet the limits for the permissible mean residence time. It is essential to build up a pressure gradient that is as uniform as possible over the entire length of the pipe. At pressures of 5 to 500 mbar, preferably 50 to 350 mbar, working without an inert gas is possible. The usual work-up temperatures during the work-up of the resin in a coiled tube evaporator are 140-240 ° C, but preferably 170-215; the mean residence times are 5-120 sec, but preferably 10-40 sec. The speed of the gases formed from solvent vapor and the vapor of the monomers formed during the workup by esterification of the alkyl borate esters is 30-200 m / sec; - In extreme cases at the evaporator outlet it reaches the speed of sound.

This steam also serves as the driving steam for the resin melt and thus enables the rapid transport of the liquid resin through the coiled evaporation and reaction tube (snake tube) in the specific short residence times inherent in the method according to the invention and determined by the dimensions of the apparatus.

The thermal load on the reactive resin is kept so low during the workup due to the short residence times in the coiled tube that undesired crosslinking reactions do not occur or only to a minor extent, but a solvent-free but highly reactive reinforcing resin is obtained due to the trifunctional boric acid alkyl novolakester groups.

65-90% by weight solutions of the boron-containing phenol-formaldehyde resins are preferably subjected to the isolation process according to the invention.

When the resin is evaporated in the reaction kettle or in a screw, between 12 and 20% by weight of the boric acid ester compounds used are recovered in the distillate. Due to the short-term but relatively high temperature load possible in the snake tube, the added boric acid ester components are better reacted with the novolak, so that only 6-10% by weight of the boric acid esters used are found in the resulting distillate and the reinforcing resins obtained in this way have an optimal hardness effectiveness unfold the rubber materials hardened with it.

The reprocessing method according to the invention is also advantageous with regard to the simple controllability of the product properties by means of the vacuum set. Since the vacuum set at a constant temperature and constant throughput determines the amount of steam, its speed and thus the conveying speed of the liquid resin, the residence time of the resin within the evaporator is regulated even with certain constant device dimensions.

The product properties of the resin can thus be significantly determined and easily optimized by simply varying the pressure used in the processing. This is not possible with any of the aforementioned processing methods within a sufficiently small residence time spectrum.

The reprocessing method according to the invention using a snake tube evaporator of the above. Apparatus constants allow the boric acid ester-modified, highly reactive phenol-formaldehyde resins, which are effective as reinforcing resins for rubbers, to be economically isolated from their solutions at high throughputs at high throughput rates.

• In der beiliegenden Zeichnung ist die Apparatur prinzipiell dargestellt. Aus der mit 80-120°C, vorzugsweise 80-100°C, beheizten Vorlage (1) wird die ca. 75 Gew.-%ige - hier isobutanolische - Harzlösung über die Pumpe (2) dem gewendelten Rekations- und Verdampfungs-rohr (3) zugeführt. Nach der Pumpe bzw. vor dem Schlangenrohrverdampfer beträgt die Temperatur der Harzlösun_g 170-220°C, vorzugsweise 190-210°C, und der Druck wird am Schlangenrohrende auf 50-500 mbar, vorzugsweise 100-300 mbar eingestellt. Die eingedampfte Harzschmelze aus dem Zyklon (4) wird über die Pumpe (5) einer Kühlung und anschließend einer geeigneten Konfektionierungsapparatur wie einer Kühlwalze oder einem Pastellierband zugeführt, während die Lösungsmitteldämpfe in einem Kondensator (6) abgeschieden werden. Das Kondensat wird durch Leitung (7) abgeführt. Die Pumpe (8) erzeugt das Vakuum.

Description of a suitable apparatus for isolating the resins from their solutions:

• The apparatus is shown in principle in the accompanying drawing. From the template (1) heated at 80-120 ° C, preferably 80-100 ° C, the approx. 75% by weight - here isobutanolic - resin solution is pumped (2) into the coiled recation and evaporation pipe (3) fed. After the pump or upstream of the coil evaporator, the temperature of the resin solution is 170-220 ° C, preferably 190-210 ° C, and the pressure at the coil end is set to 50-500 mbar, preferably 100-300 mbar. The evaporated resin melt from the cyclone (4) is fed via the pump (5) to cooling and then to a suitable packaging apparatus such as a cooling roller or a pasting belt, while the solvent vapors are separated in a condenser (6). The condensate is discharged through line (7). The pump (8) creates the vacuum.

The dimensions of the coiled tube, which are dependent on the throughput and are necessary for achieving reinforcing resins of suitable optimal quality, with which the resin insulation process according to the invention can be carried out, are listed as examples in the following table:

• In die Reaktion eingesetzt wird das bei der Bisphenol-A-Herstellung anfallende "Primärharz", ein Mehrkernphenolgemisch aus Bisphenol-A-Isomeren mit Hydroxyphenyl-hydroxyindan- und Hydroxyphenyl-hydroxychroman-Isomeren im Gewichtsverhältnis von ca. 7:1:1.

The resin solution on which the following examples are based was obtained in accordance with DE-OS 2 557 613 in the following manner:

• The "primary resin" obtained in the production of bisphenol A, a multinuclear phenol mixture of bisphenol A isomers with hydroxyphenyl-hydroxyindane and hydroxyphenyl-hydroxychroman isomers in a weight ratio of about 7: 1: 1, is used in the reaction.

890 kg of "primary resin" are dissolved in 200 kg of isobutanol and adjusted to pH = 2 with 35 kg of 85% by weight phosphoric acid and 2 kg of p-toluenesulfonic acid at 80 ° C. It is filtered through a pressure filter and 220 kg of 30% by weight formalin and 97 kg of the unsaturated fatty acid "Edenor UKD" (from Henkel, Düsseldorf / Germany) are metered in at the same time, heating to boiling under a nitrogen atmosphere and stirring (internal temperature: 97 ° C). After a reaction for 1 hour, 190 kg of water are distilled off azeotropically, the internal temperature rising to 127.degree.

anschließend 80 kg Isobutanol sowie 10 kg Wasser abdestilliert, wobei die Innentemperatur des Reaktionsgemisches auf 147°C ansteigt. Der Feststoffgehalt der aufarbeitungsfertigen Harzlösung beträgt ca. 75 Gew.-96.300 kg of a separately prepared liquid boric acid isobutyl ester anhydride of the composition are added to the reaction mixture

80 kg of isobutanol and 10 kg of water were then distilled off, the internal temperature of the reac tion mixture rises to 147 ° C. The solids content of the resin solution ready for processing is approximately 75% by weight.

Example 1

• 150 kg der Harzlösung wurden bei bis auf 150°C ansteigender Temperatur erst bei Normaldruck und anschließend unter vermindertem Druck (bis 400 mbar) unter Rühren eingeengt (man erhält 28 kg Destillat). Das flüssige Harz wurde abgelassen.
• Borgehalt des Destillats: 1,9%
• Ep. des Harzes (nach DIN 53180): 63°C
• Borgehalt des Harzes: 1,6%

Processing the reinforcement resin solution by evaporation in the boiler:

• 150 kg of the resin solution were concentrated at a temperature rising to 150 ° C. only under normal pressure and then under reduced pressure (up to 400 mbar) with stirring (28 kg of distillate are obtained). The liquid resin was drained.
• Boron content of the distillate: 1.9%
• Ep. Of the resin (according to DIN 53180): 63 ° C
• Boron content of the resin: 1.6%

The resin sintered together during grinding. If you choose evaporation temperatures _> 150 ° C and _< 180 ° C, crosslinked, infusible resins are obtained after the distillation of 37 kg of solvent.

Example 2

• 100 kg der Harzlösung wurden in einer 2-Wellen-Ausdampfschnecke bei bis auf 155°C ansteigender Temperatur und ca. 50 mbar eingedampft. Destillatmenge: 24 kg. Das resultierende Harz war teilvernetzt und konnte auf Einmischwalzen nicht homogen in den Kautschuk eingemischt werden.

Working up the reinforcing resin solution by evaporation in a screw:

• 100 kg of the resin solution were evaporated in a 2-shaft evaporation screw at a temperature rising to 155 ° C. and about 50 mbar. Amount of distillate: 24 kg. The resulting resin was partially cross-linked and could not be mixed homogeneously into the rubber on mixing rollers.

• Ep. (DIN 53180): 61 °C
• Borgehalt des Harzes: 1,6-1,7%
• Borgehalt des Destillats: 1,6%
• (Destillatmenge: 20 kg/100 kg Harzlösung)

If you choose processing temperatures of maximum 130 ° C and a pressure of 46 mbar, you get a resin with the following characteristics:

• Ep. (DIN 53180): 61 ° C
• Boron content of the resin: 1.6-1.7%
• Boron content of the distillate: 1.6%
• (Amount of distillate: 20 kg / 100 kg resin solution)

Example 3

• Destillat: 122 kg
• Borgehalt des Destillats: 0,7%

Working up the reinforcing resin solution by evaporation in a coiled tube evaporator with A = 0.226, B = ₁ 90; 500 kg of the resin solution were in a coiled tube evaporator with tube length L = 4.5 m and cross section Q = 176 mm ² at a throughput of 40 kg solution / hour. and worked up at a temperature of 190 ° C and a pressure of 200 mbar.

• Distillate: 122 kg
• Boron content of the distillate: 0.7%

• Ep. (DIN 53180): 74°C
• Borgehalt: 1,8-2,0%

The resin obtained had the following characteristics:

• Ep. (DIN 53180): 74 ° C
• Boron content: 1.8-2.0%

Claims (9)

1. A process for isolating boron-containing phenol/formaldehyde resins from their reaction media which, in addition to the end product, also contain starting compounds and solvents used, characterised in that isolation is carried out by concentration through evaporation in a spiral flow evaporator which has the following characteristics:

2. A process according to Claim 1, characterised in that the characteristics of the spiral flow evaporator are as follows:

A = from 0.2 to 0.5 and

B =from 150 to 300.

3. A process according to Claim 1 and 2, characterised in that the isolation process is carried out at temperatures in the range of from 140 to 240°C.

4. A process according to Claims 1 to 3, characterised in that the isolation process is carried out at temperatures in the range of from 170 to 215°C.

5. A process according to Claims 1 to 4, characterised in that the mean residence time of the resin in the spiral flow evaporator amounts to from 5 to 120 seconds.

6. A process according to Claims 1 to 5, characterised in that the mean residence time of the resin in the spiral flow evaporator amounts to from 10 to 40 seconds.

7. A process according to Claims 1 to 6, characterised in that evaporation is carried out in the presence of an inert gas.

8. A process according to Claims 1 to 7, characterised in that the spiral flow evaporator is under a pressure gradient of from 5 to 500 mbars.

9. A process according to Claims 1 to 8, characterised in that the spiral flow evaporator is under a pressure gradient of from 50 to 350 mbars.

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